Spain and the Canary Islands are basically destinations for all seasons. While the interior can be uncomfortably hot in the summer, it is wonderfully pleasant along the coast.
The north-west of Spain has a distinct maritime climate. The winter is mild and rainy. The summer is wet and relatively cool. The maximum temperature is around 20 degrees. The interior of Spain has a dry continental climate. The summer is long and hot. The winter is short but cold. The coast of southern and eastern Spain has a Mediterranean climate with dry, hot summers. The mild winters are good for the winter. The Guadalquivir basin in Andalusia is notorious for the summer heat. Seville is the hottest city in Europe. Temperatures above 40 degrees occur in the summer. The rainfall mainly falls in the fall and winter. The Costa Brava is pleasantly warm in the summer, not too hot. In the winter it is a bit too cool to spend the winter pleasantly.
Take along light clothing. You need a (fleece) sweater or cardigan for those cool evenings. Long sleeves and long pants offer protection against mosquitoes in the evening. Sturdy hiking boots also offer protection against snake bites. You need sturdy sandals on the coast. Water shoes with a sturdy sole protect against sharp stones and rocks. In religious buildings you must adhere to the dress code. Women wear their skirts or pants over their knees and the arms are completely covered. Men wear long pants and the arms are covered to the elbow.
On Mallorca you risk a fine between € 50 and € 200 if you are only staying in a public area (supermarket, bar, restaurant, terrace), dressed in a bikini or swimsuit. This does not apply to beaches, boulevards and adjacent streets.